The present invention relates to a hand held instrument having a working element, such as a drill bit, to carry out some function on a work piece and more particularly, to a hand held instrument having a pressure sensor to determine the pressure between the working element and the hand held instrument.
There are numerous differing types of hand held instruments that are in use or have been proposed to apply a working element to some work piece. Those instruments can include a normal hand drill for use by an individual or one of many hand held devices that are used in the dental field including but not limited to, a dental drill, a Cavitron instrument for cleaning teeth and a dental laser.
In any case, the instrument is a hand held instrument and there is some power source that provides a power to operate a working element that is located at the distal end of the instrument. The source of power may be a source of rotational power, as is used with a dental drill, an electrical signal as is used with a vibrating tooth cleaning device, a pressurized source of gas such as is used in a turbine powered dental drill or other source of power.
In such hand held instruments, there is also normally some switching device located in close proximity to the user that can be manually operated by the user in order to apply the source of power to activate the working element to carry out some procedure. Such switching devices can include devices that are, for example, foot operated switches or some switching device that is located on the hand held instrument itself. In such present switching devices, however, it is necessary for the user to take some deliberate, manual action to activate a switch to connect the source of power to the working element to carry out the function of the working element of the hand held instrument. The user is, at the time of the switch activation, concentrating on the target for the working element and it can be distracting to require some physical activation of a switching device with the hand or foot of the user in order to activate the working element.
Accordingly, it would be advantageous to have a switching system or device that can activate the working element automatically without the need for the user to actually push or otherwise take some potentially distracting action to operate a switching device to commenced the action of the working element so that the user can more fully concentrate on the location and use of the working element as it is applied to the target work piece.
In addition, there is another feature of present hand held instruments that is currently lacking and which could enhance the use of such instruments to the user. Using the example of a dental drill, in the drilling of a patient's tooth to carry out a procedure in filling a cavity, the user normally engages the working element of the dental instrument to the tooth enamel and moves the working element inwardly with respect to the tooth in working on the cavity. There is a point in the procedure where the drill bit passes through the hard outer enamel of the tooth and enters the softer material that comprises the pulp cavity of the tooth and, at that point, there is a lessening of the pressure on the working element since the drill is now entering the less dense portion of the tooth i.e. the cavity.
While the user can normally feel that transition from the harder material of the enamel to the softer material, it would be advantageous to have some visible or audible indication that would alert the user that the drill bit has passed through the hard enamel and has reached the less dense material of the pulp cavity.